Pain is the single most common symptom for which patients seek medical treatment and there is currently no objective method available for its measurement. Present methods of quantifying “pain” are little more than lexicons for its verbal description or biomechanical methods for measuring the restriction of a particular range of motion or activities of daily living associated with the pain. Some psychometric methods attempt to quantify the personality or cognitive distortions from which the pain patient suffers. In no case, however, do these methods reveal the covert and subjective sensory perception that is the pain experience in a way that can be quantified by an outside observer (for review, see Lipman J J. Chapter 9: Pain Measurement In: Contemporary Issues in Pain Management. Parris, WCV (ed.) KLUWER Pubs., (1991)). The need for pain measurement methods was recently addressed by both the Social Security Administration and the United States Congress. A report ordered by Congress through the Secretary of Health and Human Services by a Commission on the Evaluation of Pain, recommended that an objective measurement of pain be developed to assist in determining disability (see Fordice, Back Pain in the Workplace: Management of Disability in Nonspecific Conditions-Task Force on Pain in the Workplace, (I.A.S.P. Press, Seattle, 1995); Fields, Core Curriculum for Professional Education in Pain: Task Force on Professional Education, (I.A.S.P. Press, Seattle, 1995); American Pain Society, Principles Of Analgesic Use In the Treatment of Acute Pain and Chronic Cancer Pain-a Concise Guide, (American Pain Society, Washington D.C., 1990)).
The need for objective pain measurement goes beyond the economics of forensic disability assessment. Objective methods of pain measurement are required for accurate assessment of patient complaint and to assure appropriate treatment. For example, the need to appropriately medicate severe acute and chronic pain and also cancer pain requires an objective method of pain measurement. A corollary need is to avoid inappropriate treatment of pain—or claimed pain—where the possibility of malingering for secondary gain is a possibility. Such “secondary gains” are believed to account for an appreciable portion of chronic pain treatment demand, and forensically include the desire for disability payments, for insurance damage settlements or for other fiduciary incentives. Such secondary gains are not always conscious and may derive from psychological reasons related to the psychosocial set and setting of the patient and their disease. The inappropriate desire for opiate drugs probably accounts for a significant fraction of pain therapy prescription drug demand. Yet absent any objective method of establishing the existence of “pain”, the physician has no objective standards by which to prohibit such demand, and frequently feels ethically bound to take claims of pain at face value, or risk accusation of ineffective care and inhumane treatment.
Furthermore, an objective pain measurement device that is operable in the general practitioner's office would fulfill a pressing diagnostic need. It is from the general practitioner's office that referrals to neurologists and other specialists are made. For example, patient complaints of subjective numbness are often not detectable on clinical examination because present diagnostic methods are not sensitive enough to detect the early stage sensory impairments of such neurological disorders as nerve root entrapment or peripheral neuropathy. As a result, patients with these types of neurological disorders cannot be diagnosed until the disorder progresses to a detectable level. The availability of a pain measurement device sensitive enough to detect the presence or absence of these and other abnormalities at an early stage would provide more effective medical intervention, or avoid unnecessary medical intervention. In order for such a device to be cost-effective for the general practitioner it should not require valuable dedicated space, and thus should be portable. Similarly, greater cost-effectiveness would be realized if the device were operable by a single person, unaided.
Basic psychophysical methods for the estimation of pain sensibility have a long history of questionable clinical relevance. Psychophysical methods seek to quantify pain intensity in an objective fashion despite the fact that pain is a complex and multi-faceted sensory mode, intrinsically containing dimensions of set, setting, ideation, memory, anxiety, and experiential import.
Subjective pain perception does not bear a simple relationship to stimulus intensity, but it nevertheless has some quantifiable dimensions and limits: a lower level of identity (the pain threshold) and an upper level of identity (the tolerance level). Below the pain threshold, stimuli of increasing intensity destined to broach this level are perceived as noxious yet non-painful (prepain). The pain threshold itself is highly labile and subject to psychological manipulation either of imposed suggestion (experimenter bias) or autosuggestion bias (the placebo response) or both. No studies have been able to demonstrate a relationship between pain threshold and the underlying pain state; in fact, pain threshold measurement procedures are unable to quantitatively demonstrate analgesic states engendered by clinically proven drugs as, for example, morphine (for review, see Chapman et al. “On the Relationship of Human Laboratory and Clinical Pain Research,” Pain Measurement and Assessment, pp. 251-257 (Raven Press, New York, 1983)). Furthermore, the method suffers from major disadvantages when transferred to the clinical situation where the test subject, who may suffer excruciating pain of endogenous pathological origin, is less able to attend to the minor sensory nuances of the pain threshold.
The pain sensitivity range constitutes a psychophysical region between the pain threshold level, where prepain becomes subjectively painful, and the pain tolerance level, which represents the greatest intensity of a noxious stimulus that a subject can tolerate (Hardy, Wolff and Goodell in Pain Sensations and Reactions (Williams and Wilkins, Baltimore, 1952)). In contrast to the pain threshold level, the pain tolerance level is subjectively distinct and unequivocal. Further, the pain tolerance level exhibits a linear change with stimulus intensity and yet it shares a sufficient commonality with the physiological processes of endogenous pathological pain perception that are positively influenced by changes in the endogenous pain state.
Pain tolerance levels are usually assessed by the use of a continuous, rather than a discrete, noxious stimulus, the cut-off of which is always the maximum limit of the subject's subjective pain tolerance. Pain tolerance has been measured by several means including the cold pressor test in which the hand or a limb is immersed in ice water until unendurable pain results, focal pressure, tourniquet ischemia and radiant heat (For review see Lipman J. J., “Pain Measurement,” supra). Tolerance methods using these techniques, unlike threshold methods, also evoke some not inconsiderable anxiety and apprehension on the part of the subject, which may resemble the anxiety of the pain-suffering patient. However, studies have shown that tactile stimulation interferes with that aspect of cutaneous tolerance limit responsive to internal pain interference and thus methods that utilize a contact stimulus invalidate pain tolerance level results. Another method that has been developed uses hot air to generate heat in a subject (Muller et al., German Patent 92,04,961 (1992)). However, hot air, like the methods described above, generates contact stimulus, since heated moving air molecules stimulate mechanoreceptors found on the skin. Furthermore, this apparatus utilizes a temperature probe that makes contact with the skin near the site that is heated. Therefore, this apparatus cannot be used to accurately measure pain tolerance. While the cold pressor, focal pressure, tourniquet ischemia, and hot air tests all involve tactile stimulation, radiant heat methods do not require direct contact with the subject.
The concept of a radiant heat pain stimulator for human use was initially developed by Hardy, Wolff and Goodell in 1952 (Pain Sensations and Reactions (Williams and Wilkins, Baltimore, 1952)). However, most radiant heat pain stimulators have been designed to measure the pain threshold level and thus are prone to the disadvantages inherent in such measurement. Hargreaves et al. describe a radiant light/heat projector used as a thermal stimulator for use in testing both animals and man (U.S. Pat. No. 5,025,796 (1991)). However, all of the embodiments disclosed in Hargreaves et al., like the non-radiant heat apparatuses described above, involve tactile stimulation, since the subject must rest on a base to allow the radiant heat to be focused. Thus, pain tolerance results obtained with the instrument are invalid. Recently, a concept prototype heat pain stimulator was developed that measures the pain tolerance level (see Lipman et al., Pain 30, 59-67 (1987); Lipman et al., Pain 39, 249-256 (1989); and Lipman et al., J. Neurosurg. 72, 883-888 (1990)). The concept prototype was a nonportable, electromechanical device that did not allow for automatic data acquisition. As such, the concept prototype required dedicated laboratory space and also required one person to operate the device and a second person to record data. Accordingly, there remains a need in the art for a particular non-contact, radiant heat beam dolorimeter that provides a quantitative, objective measure of the pain tolerance level and allows for automatic data acquisition.
In applications such as a heat beam dolorimeter, where electromagnetic radiation (EMR) projected from an emitter is directed at a target, a feedback mechanism would be helpful to accommodate conditions where distance may undesirably change between emitter and target. Such a feedback mechanism might use a sensor, positioned at or within the target, to feedback-control either the power output or position (i.e., the emitter-target distance) of the emitter, thus ensuring that these characteristics of the emitter are rapidly and automatically adjusted to maintain target and/or sensor irradiation within set limits. Unfortunately, available sensor response characteristics are largely inadequate to this task. Thus, should a temperature sensor within the target be used to feedback control, for example, a motor-drive positioning mechanism on which a radiant heat projector (emitter) is mounted, whereby feedback from the sensor is used to control projector position, either toward or away from the target, it is found that accurate, rapid and responsive positioning of the emitter by the motor drive cannot be achieved because the sensor response time is invariably too slow, having too much inertia or resistance to change. The same is true of light and other forms of EMR. Therefore there is a need for automatic control processes that regulate the delivery rate of the EMR received at the target by adjusting the output of the emitter mechanism, the projector of heat or light or other EMR.
When the emitter is employed as a sensory stimulator for testing human cutaneous sensibility, such as a heat beam dolorimeter for determining pain tolerance as described above, it is essential that the energy delivered to the skin be precisely controlled. Since delivered energy is a proportional function of the power of the emitter and the distance of the emitter to the skin target, both must be held constant to achieve adequate stimulus control. Therefore, there is a need for improved automatic control processes that regulate the delivery rate of heat received at the target site of a patient's skin in heat beam dolorimeter applications. The present invention provides a sonar-based automatic-control system which overcomes these problems.
Pain management has only recently come into being as a specialty discipline in its own right; the American Academy of Pain Management (AAPM) was founded eleven years ago, for instance. Pain, described as an “epidemic” by AAPM, affects millions in the United States: 50 million Americans are partially or totally disabled by pain and 45% of all Americans seek care for persistent pain at some point in their lives (American Pain Society, American Academy of Pain Management, Janssen Pharmaceutical: Chronic pain in America: Roadblocks to relief, Study conducted by Roper Starch Worldwide (1999)).
The problem of undertreatment is however particularly topical since the recent introduction of new regulations governing hospital practice promulgated by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO). These regulations came into force Jan. 1, 2001, and mandate clinic and hospital practices that are designed to both avoid undertreatment and to document affirmative medical pain-relief interventions. Health care providers must document their compliance with the directive. This invention provides an inexpensive computerized device, which meets these needs.
Educational initiatives are currently being introduced throughout both medical/nursing training and established practice to introduce the JCAHO mandates pertaining to clinical care. This initiative continues and enforces the earlier and continuing efforts of the International Association for the Study of Pain (IASP) and the AAPM into raising physician and nurse awareness of the need for humane treatment of pain and promoting the doctrine that pain is often unnecessary and avoidable with appropriate drug treatment. Specific recommendations include pre-emptive analgesic therapy, regular—timed—rather than PRN drug administration, and a general overhaul of historically unhelpful attitudes concerning the ‘addictiveness’ of opioids given for pain relief. (See, the management of chronic pain in older persons: AGS panel on chronic pain in older persons. J. Am. Geriatric Soc. 46(5):635-651 (1998)).
The core need in any pain management strategy is an effective method for assessing the subjective pain state of the patient, and of measuring changes in this state in response to treatment. Currently a variety of simple verbally administered or paper-and-pencil Pain Questionnaires (PQs) that the patient completes at intervals are used. Their currently remains a need for computerized PQ methods that satisfies the needs of both patients and health care providers, and simultaneously satisfies the JCAHO documentation requirements.
As described recently by Bellamy (1999) in a comparative evaluation of pain questionnaire methods, simple scaling methods (category and visual pain analog scales) are more responsive for assessment needs than complex ones (such as the McGill Pain Questionnaire) and defeat the latter's inter-cultural disadvantages of linguistic biases. (Bellamy, N. (1999) Comparative study of self-rating pain scales in osteoarthritis patients, Current Medical Research and Opinion 15(2):113-119). The demands of clinical practice further require that a pain assessment tool be (1) brief, (2) simple, (3) rapid to complete and (4) easy to score. (Bellamy N, Kaloni S, Pope J, Coulter K and Campbell J (1998) Quantitative rheumatology: A survey of outcome measurement procedures in routine rheumatology outpatient practice in Canada, J. Rheumatol. 25, 852-858; Bellamy N, Muirden K, Brooks P M et al (1998)). The JCAHO guidelines also provide that the method provide a measure of health-care provider compliance. It follows that the method should be capable of centralized data accession to this end. A final requirement suggested by the need to render the device practically useful to the nurse and physician is that it provides a statistical output of pain response to therapy both printable and immediately accessible at any time.
An early review of the need for, and the methods employed in, clinical pain measurement is found in Lipman et al. 1991. (Lipman J J. Chapter 9: Pain Measurement In: Contemporary Issues in Pain Management. Parris, WCV (ed.) KLUWER Pubs., (1991)). Pain, an entirely subjective phenomenon, is assessed either by indirect behavioral observation methods or by direct interrogation methods—the latter typically administered in the form of a pain questionnaire (PQ). These are of varying degrees of complexity—from the McGill Pain Questionnaire (MPQ) which takes about five to ten minutes to complete, to the simple Visual Pain Analog Scale (VPAS) which takes seconds to complete.
Pain questionnaire (PQ) methods seek to present the pain continuum as a metaphor—either linguistic, spatial, facial or otherwise—which the patient can endorse in such a manner as to relate the degree of their present pain or its relief. The range of metaphors is quite extensive, but in summary these are in typology either ordinal or category and either verbal or printed in form
Verbal descriptor scales are commonly employed for pain assessment by asking the patient to rate their present pain on a numerical rating scale from one to one hundred or some other number: for instance, the NRS-101 asks the patient to scale their pain between one and a hundred and one but verbal enquiry has the serious disadvantage that the questioner (nurse or doctor) inevitably conveys expectation by voice, tone, facial expression, and demeanor, which will inevitably influence the patient's response. This face-to-face method is capable of engendering bias; indeed, it has been used by investigators studying the placebo response as a means of deliberately provoking the unconscious expectation of pain relief. (Lipman J J, Miller B E, Mays K S, Miller M N, North W C and Byrne, W L. (1990) Peak “B” Endorphin Concentration in Cerebrospinal Fluid: Reduced in Chronic Pain Patients and Increased During the Placebo Response. Psychopharmacology 109 (1) 112-116.) For this reason, in an attempt to place distance between the conscious or unconscious expectations of the questioner and the response of the patient, printed questionnaires are commonly preferred.
Printed ordinal metaphors such as the aforementioned visual pain analog or mood scales (VPAS or VMAS scales, respectively) provide on a printed page (or in the present case, a computer screen) a line (typically, historically and by convention 10 cm long) bounded by words that define the sensory continuum being measured. For the VPAS these words are, on the left, ‘no pain’ and on the right, ‘maximum possible pain.’ The patient indicates their present pain intensity by marking the line at the appropriate point (see FIGS. 2 and 4). By imposing index marks (usually 10, every centimeter or 1/10th of the line) on the VPAS, the analog is converted into a category scale—with ten predetermined locations available for marking by the patient. Other category scales employ words arranged along a rank order continuum (e.g., ‘no pain’, ‘a little’, ‘some’, ‘a lot’, ‘terrible’) from which the patient may choose, and others employ nonlinguistic categories, such as the facial scale (used with pediatric or nonverbal patients) which presents a series of faces with stylized expressions representing the range from ‘unhappy’ at one end to ‘happy’ at the other.
One advantage of category scales when employed to ask the patient how they are feeling ‘now’ compared with ‘before’ (when they completed the scale previously) is that it is easy for the patient to recall their earlier response—limited as it was to a predetermined choice from a small number of choices. However, when used to ask the patient to rate their present degree of pain without regard to any earlier response they may have made, this property of category scales proves somewhat of a disadvantage—since it is hoped in this situation that the patient's present response will be uninfluenced by prior responses. For this reason, a simple unmarked 10 cm VPAS line is generally preferred for present pain assessment. Within certain limitations, the VPAS is a reliable way of polling opinion on a unidimentional axis and it has the advantage of being quick and easy to do, is easily understood by the patient, is readily scored (using a ruler when the test is printed) and has long been validated against other polling methods whilst retaining current validity and popularity (Scott J, Huskisson E C (1976) Graphic representation of pain, Pain 2(2):175-184; Joyce C R, Zutish D W, Hrubes V et al (1975) Comparison of fixed interval and visual analog scales for rating chronic pain, Eur. J. Clin. Pharmacol. 8:415-420; Downie W W, Leatham P A, Rhind V M et al (1978) Studies with pain rating scales, Ann. Rheum. Dis. 37:378-381; Melzac R and Katz J (1994), Chapter 18: Pain measurement in persons in pain in Wall P & Melzac R (eds) Textbook of Pain, Churchill Livingston pp337-351).
Category scales, as mentioned above, present the patient with a limited number of choices of descriptor words to express their current pain intensity or pain relief. Scoring is by means of assigning a number to each category. Thus, on the five-category Pain Severity (PS) scale ‘no pain’ is assigned a score of ‘0’, ‘a little pain’ has a score of ‘1’, ‘some pain’ has a score of ‘2’, ‘a lot’ has a score of ‘3’ and a score of ‘4’ is assigned to the category of ‘terrible pain’. These numbers are of course completely arbitrary in quantity though not in rank order, and hence parametric statistics cannot be used to compare scores.
Category scales are most useful when employing non-parametric methods to examine within-patient and between-patient responses to pain treatment, and the ‘Pain Intensity Difference (PID)—the numerical change in category score following administration of a pain relieving drug—is a standard pharmaceutical industry tool.
Both analog and category scales are nowadays routinely employed in pain research and therapy, including surgical recovery monitoring administered as paper-and-pencil methods. (Hutchinson P J, Laing R J, Waran V et al (2000), Assessing outcome in lumbar disc surgery using patient completed measures, Br. J. Neurosurg. 14(3):195-9; Goldstein A, Grimault P, Henriqie A et al (2000) Preventing postoperative pain by local anesthetic instillation after laparoscopic gynecologic surgery: A placebo-controlled comparison of bupivacaine and ropivacaine, Anesth. Analg. 91(2): 403-407; Milligan K R, Convery P N, Weir P, Quinn P & Connoly D (2000) The efficacy of epidural infusions of levobupivacaine with and without clonidine for postoperative pain relief in patients undergoing total hip replacement, Anesth. Analg. 91(2): 393-397; Ellis J A, Blouin R & Lockett J (1999) Patient-controlled analgesia: optimizing the experience, Clin. Nurs. Res, 8(3):283-294.)
Current computer-based technology available on the market has a number of shortfalls. A peltier-type thermal pain stimulator (Medoc Instruments, Israel) for use in pain threshold measurements is available. The thermal stimulator has an accessory device that is a VPAS-type ‘mechanical slide rule,’ called the Computerized Visual Analog Scale, or COVAS, which the patient employs, by moving the mechanical cursor, to indicate the degree of thermal pain the peltier thermode has evoked during an examination. The software driving this accessory is inherent to the thermode program and cannot in its present form be modified to stand alone as a patient assessment tool. The Medoc device is hardware limited, in that it administers only one PQ test (the COPAS), and only in conjunction with the sensory testing protocol, and only by employing the ‘slide switch’ interface. No provision exists to incorporate nurse input or to administer Mood, Pain Relief, Pain Intensity or other scales.
Another device on the market, a software program called Back Pain Monitor (BPM, Avenet, Europe) is available and is used as a comprehensive pain and disability assessment tool for back pain patients—administering questions regarding pain status to which the patient themselves responds, and questions regarding posture, mobility and performance to which a trained therapist responds. The BPM device is likewise by design and construction limited to its present purpose and takes several minutes to complete all the questionnaire forms.
Periodic delivery of paper forms of pain questionnaires are known in the art.
The current invention meets the many needs discussed above. The software and device of the current invention enables hospitals to meet JCAHO mandates for pain control documentation—introduced on Jan. 1, 2001—and additionally provide a documentation method for demonstration of treatment efficacy of use in reimbursement justification and pain therapy (including drug) research.